1. Field of the Invention
The present invention relates to a hinge, and more particularly to a hinge preferably applicable to a foldable electronic device and capable of gradually opening or closing a cover of the foldable electronic device.
2. The Related Art
As the development of modern mobile communication industry, portable electronic devices such as cellular phones, notebook computers and personal digital assistants etc., become more and more popular. Thereinto, many portable electronic devices have a function of displaying images. In order to display images as distinctly as possible, so screens of the portable electronic devices need to be designed as big as possible. But it is not convenient to carry the portable electronic device with a big screen. That is, the required big screen and the required small size of the portable electronic device are contrary. To solve the problem, foldable electronic devices have been developed. Generally, the foldable electronic device has a cover which is usually used as a screen, and a main body which is joined together with the cover by some types of hinge allowing the cover to be unfolded from the main body.
FIG. 10 shows a conventional hinge used in a foldable electronic device which has a cover and a main body. The hinge includes a cylindrical shaft 700. One end of the shaft 700 is received in a rotatable cam 600 and the other end of the shaft 700 extends to pass through a sliding cam 500, a housing 300 and a cap 200, and is located in the cap 200 through a ring 100. The rotatable cam 600 protrudes downward to form two pushing portions 601 at opposite sides thereof. The sliding cam 500 slideably received in an end of the housing 300 defines two concave grooves 501 receiving the pushing portions 601 respectively. A spring 400 is received in the housing 300 between the sliding cam 500 and the cap 200 plugging an opposite end of the housing 300 and extending toward an inner of the housing 300 and encircles the shaft 700. One end of the spring 400 is fixed on the sliding cam 500, and an opposite end of the spring 400 is mounted on the cap 200. If a user would like to open the foldable electronic device, the user shall firstly unfold the cover from the main body to an angle. The force that the user provides pushes the pushing portions 601 to the top of the concave grooves 501. At the same time, the sliding cam 500 is compelled to slide toward the inner of the housing 300, and then the spring 400 is compressed. Then, the user stops acting on the foldable electronic device, and the elastic force of the spring 400 drives the foldable electronic device opened fully.
However, the movement that the spring 400 releases the elastic force to open the foldable electronic device is quick and uncontrolled, so the impact is produced between the cover and the main body. In this case, the foldable electronic device is easy to be broken or damaged. Thus, a highly reliable hinge is desired to overcome the disadvantage mentioned above.